Specifications for visitor filters to be used in LRS
Gary J. Hill, April 2002
Several positions are available for custom/visitor filters to be used in
LRS on a temporary basis. Filters can be used for imaging, or as blocking
filters for spectroscopy. Spare filter holders are available, which will
accommodate circular filters with the following characteristics:
- Diameter: 100 (+0.0/-0.3) mm
- Thickness: 8 mm
- Flatness: 1 wave per inch or better, 1 arcminute maximum wedge
- Clear aperture 85% (85 mm)
The thickness can't be less than 5 mm or more than 10 mm. Thinner filters
will not allow the instrument to focus, and thicker are not accommodated by
the holders. If there is demand, we can create holders that will accept
4.0 inch diameter circular filters, but we will need 6-8 weeks notice.
In order to use a custom filter in LRS, it must be mounted in a spare
position, and the focus offset for the filter must be determined. It should
have a unique name, to identify it in the ICE software, which should have
fewer than 8-9 characters (this limit is to save the RAs having to type a lot).
Spaces are not allowed in the identifying name.
If custom filters are being ordered from a manufacturer, we recommend the
following specifications in addition to the bandpass and size:
- blocked less than 10^-3 from 0.35 to 1.2 microns
- hard AR coating
- no visible pinholes (for use with CCD detector)
- this is for interference filters
- will be used at 10 Celceus, normal incidence in f/5 beam
- sealed on the edge with no light leaks and marked with the name
- transmission curves to be supplied
Specific questions can be directed to Gary Hill at:
hill@astro.as.utexas.edu